I have been in the same boat that is why my stocking is going slowly. I have trouble finding males at lfs
. I hit them often and buy them when I can. It's also the reason why I have ended up with smaller tanks holding juvies and females. I have done pretty well picking out males from unsexed fish. I usually go with the largest/most aggressive in the tank. I currently do have a few females in my grow out tank but colors are starting to come in on several of my juvies. I think I got 8 out of 10 on my last group. I also don't have the heart to cull but I checked last time I hit the store and they said they are willing to take them. Going to wait a little longer to make sure they are females though. The hardest part is waiting. I bought a bunch of juvies 3 months ago and they are just starting to show color.